In a conventionally known vehicle sun roof system, an opening of a vehicle roof is normally closed by a sun roof panel, and can be opened either by tilting up the rear end of the sun roof panel or by tilting down the sun roof panel and sliding the sun roof panel rearward. See U.S. Pat. No. 5,718,472.
The sun roof panel is typically fitted with a pair of brackets on a lower surface thereof along either lateral edge thereof, and each bracket is supported by a pair of sliders disposed one behind the other which are in turn slidably supported, respectively, by a guide rail extending along the corresponding side of the opening. The sliders are moved along the guide rails by being pushed and pulled by a cogged cable, and are each incorporated with a mechanism for lifting and lowering the sun roof panel as required.
More specifically, when the sun roof panel is at its fully closed position, and the cable is actuated in the forward direction, the link mechanism causes the rear end of the sun roof panel to be raised (tilt up position). Conversely, when the sun roof panel is at its tilted up position, and the cable is actuated in the rearward direction, the sun roof panel tilts down to the original fully closed position. When the cable is actuated further in the rearward direction, the sun roof panel is lowered to a position (tilt down position) clear from the roof panel owing to the action of the mechanism and is then slid rearward to a slide open position. When the cable is actuated forward from this position, the sun roof panel is slid forward to the original fully closed position reversing the slide opening process.
In this previously proposed sun roof system, to prevent the fore-and-aft movement of the sun roof panel at its fully closed position, the front slider fixedly attached to the sun roof panel is engaged by the guide groove of the guide rail while a pin carried by the rear slider is engaged by a substantially horizontal section of a guide slot formed in the panel bracket fixedly secured to the sun roof panel. In the tilted up position, a rectangular block formed in a support lever (link) pivotally connected to a middle part of the panel bracket is engaged by a cutout formed in the guide rail, and this prevents the fore-and-aft movement of the sun roof panel at the fully closed position thereof.
Japanese patent laid open publication No. 2001-146114 discloses a sun roof panel system that is aimed to simplify the structure for preventing the undesired fore-and-aft movement of the sun roof panel. A cam piece fixedly secured to a front part of each panel bracket is received by a vertical groove formed in a front end of the guide rail to prevent the fore-and-aft movement of the sun roof panel when the sun roof panel is at any angle between the fully closed position and fully tilted up position. When the sun roof panel is tilted down from the fully closed position, the cam piece is disengaged from the vertical groove, and is allowed to be guided along a horizontal groove formed in the guide rail.
According to this proposal, because there are only a pair of cam pieces that restrict the fore-and-aft movement of the sun roof panel, the cam piece is required to be strong enough to withstand the force acting upon the sun roof panel, and this requires an increase in the size of the cam piece and associated guide groove. Also, this restricting arrangement is effective only when the sun roof panel is between the fully closed position and fully tilted up position so that the sun roof panel is relatively unrestricted as it is tilted down from the fully closed position. The sun roof may move in the fore-and-aft direction as it is tilted down from its fully closed position, and this could not only cause undesired rattling and noises but also apply undue forces to various parts of the mechanism. In this prior sun roof system, a similar cam piece is formed on a rear part of each panel bracket, and the guide rail is formed with a notch for passing the rear cam piece into the horizontal guide groove as the sun roof panel is tilted down prior to moving rearward. Therefore, as the sun roof panel is moved rearward, the front cam piece passes this notch, and this notch may prevent the smooth movement of the front cam when the sun roof panel is subjected to vertical accelerations as is often the case when the vehicle is traveling over an irregular road surface.